Metamorphism and metamorphic
Rocks
Metamorphism: all changes
(textural/mineralogical) that take
place on a pre-existing rock(I,S,M)
in response to new conditions (P/T)
imposed on the rock which are
different
from those under which the
rocks have originally been formed.
Changes take place in the solid state
Types or Envs. of metamorphism
• Contact (thermal) metamorphism = around
magmas
• Regional metamorphism = along
subduction zones in areas of mountain
building. Rocks in these setting are
subjected to both increase in T and to
directed pressures.
Agents of metamorphism
• Heat = thermal energy
geothermal gradient
• Pressure increases at a rate of about 250-
300 bars/km of depth.
• Chemical active hot fluids (H2O, CO2 are
the most common) moving within the rocks
are capable of dissolving rocks and
precipitating others at other places
Metamorphic Rock
subduction zone and regional metamorphism
Contact metamorphism
Metamorphic Rock
Metamorphic Rock
•Shale 
slate
ï‚®
schist
(if more H&P are
added)
•Shale or granite 
gneiss
•Limestone 
marble
Metamorphic Rock
Textures
• Foliated
rocks
• = regional
• Metamorphic
• rocks
Common metamorphic rocks
Slate
http://geology.about.com/library/bl/images/blphyllite.htm
Phyllite
Garnet Schist
Garnet schist
Mica schist
Gneiss
Banded gneiss
Marble
Folded metamorphic rocks
Stages
of Coal
formation
